The present invention relates to apparatus for transferring fluid between two structures, for example two floating vessels, or a fixed offshore structure and a vessel.
Transferring fluid, particularly of a cryogenic product, between two floating vessels, or a fixed offshore structure and a vessel, is a difficult and hazardous operation when performed in open sea. Various systems for transferring fluid have been proposed. For example, UK patent 2328196 describes a system which employs a rigid arm, one end of which is fixed in an articulated fashion to a storage vessel. The other end is supported by means of a flotation tank. A receiving vessel can be moored to this end of the rigid arm to receive fluid transferred from the storage vessel. The fluid transfer system between the rigid arm and the receiving vessel may be handled by articulated rigid pipes, for example of the type described in U.S. Pat. No. 3,556,148.
One disadvantage of such a system is that when the rigid arm is connected to the floating vessel, the action of wind and waves may cause sudden changes in the separation of the arm and vessel. This may impose unacceptable loads on the fluid transfer system or even cause the arm and vessel to collide. Therefore, there is a need to improve the relative motion behaviour between the rigid arm and the recipient vessel.
A further disadvantage is that because the rigid arm is submerged, inspection, maintenance and repair operation are more difficult to carry out.